package src.dp.sequence;

public class no72 {//编辑距离

    /**
     * 1、word1[i - 1] == word2[j - 1]：当前位相等就看下一位，dp[i][j] = dp[i - 1][j - 1]
     * 2、word1[i - 1] ！= word2[j - 1]：当前位不等，3种操作
     * 增、删：操作一样，增word1相当于删word2，dp[i-1][j]+1, dp[i][j-1]+1
     * 换：两个word都从前一位更换当前数，所以+1步操作，dp[i-1][j-1]+1
     */
    public int minDistance(String word1, String word2) {
        int len1 = word1.length();
        int len2 = word2.length();
        int[][] dp = new int[len1 + 1][len2 + 1];
        for (int i = 0; i <= len1; i++) dp[i][0] = i;
        for (int j = 0; j <= len2; j++) dp[0][j] = j;

        for (int i = 1; i <= len1; i++) {
            for (int j = 1; j <= len2; j++) {
                if (word1.charAt(i - 1) == word2.charAt(j - 1)) {
                    dp[i][j] = dp[i - 1][j - 1];
                }else {
                    dp[i][j] = Math.min(dp[i-1][j-1]+1,
                            Math.min(dp[i-1][j]+1, dp[i][j-1]+1));
                }
            }
        }
        return dp[len1][len2];

    }
}
